JP4622275B2 - Impurity introduction method - Google Patents

Description

  The present invention relates to amorphization, surface modification, and an impurity introduction layer, a junction, and other objects to be processed formed using the same, in particular, a method for forming a junction for forming an electronic element on a semiconductor substrate, The present invention relates to an impurity introduction method in a bonding method for forming an electronic element on a substrate in which a semiconductor thin film is formed on the surface of an insulating substrate used for a liquid crystal panel or the like.

  For example, when forming an element region on a semiconductor substrate, a large number of pn junctions are used. In addition, an SOI (Silicon On Insulator) substrate in which a silicon thin film is formed on the substrate surface via an insulating film is widely used in various semiconductor devices such as DRAMs. Further, a glass substrate having a semiconductor thin film formed on the substrate surface is intended to reduce the size and speed of the liquid crystal panel by integrating a liquid crystal driving circuit including a thin film transistor (TFT) in the semiconductor thin film. Attention has been paid.

  Thus, when forming various semiconductor devices, a pn junction is used. As a method for forming such a pn junction, a method is conventionally used in which a p-type impurity such as boron is introduced into an n-type silicon substrate by ion implantation and then electrically activated with a halogen lamp.

  Here, a method of forming a shallow activation layer using a difference in light absorption coefficient between silicon crystal and amorphous silicon has been proposed. That is, in the wavelength range of 375 nm or more, amorphous silicon has a larger light absorption coefficient than silicon crystal. Therefore, for example, an amorphous layer is formed in advance on the surface of the silicon substrate before irradiating light, and then irradiation with light is performed to absorb a large amount of light energy and form a shallow activation layer. It is to do. In these reports, it is common to pre-amorphize the substrate surface prior to the introduction of impurities, and then introduce the impurities. For pre-amorphization, germanium or silicon ion implantation is used (see Non-Patent Documents 1, 2, 3, 4, 5 and Patent Document 1).

As a technique for introducing impurities into the surface of a solid sample, a plasma doping method is known in which impurities are ionized and introduced into a solid with low energy (see, for example, Patent Document 2). FIG. 4 shows a schematic configuration of a plasma processing apparatus used in a plasma doping method as a conventional impurity introduction method described in Patent Document 2. In FIG. 4, a substrate electrode 1 for placing the silicon substrate 2 is provided in a vacuum vessel 18. A gas supply device 19 for supplying a doping source gas containing a desired element, for example, B ₂ H _6, into the vacuum vessel 18 and a pump 20 for depressurizing the inside of the vacuum vessel 18 are provided. Can be kept at a pressure of. Microwaves are radiated from the microwave waveguide 21 into the vacuum vessel 18 through the quartz plate 22 as a dielectric window. A magnetic field microwave plasma (electron cyclotron resonance plasma) 24 is formed in the vacuum chamber 18 by the interaction between the microwave and a DC magnetic field formed from the electromagnet 23. A high frequency power supply 10 is connected to the substrate electrode 1 via a capacitor 25 so that the potential of the substrate electrode 1 can be controlled.

In the plasma processing apparatus having such a configuration, a doping source gas introduced into the vacuum vessel 18, for example, B ₂ H _6, is converted into plasma by the plasma generating means including the microwave waveguide 21 and the electromagnet 23, and the plasma 24 Boron ions are introduced into the surface of the substrate 2 by the high frequency power source 10.

As a method for electrically activating ions such as introduced boron ions, a method of irradiating xenon flash lamp light, all solid state laser light, excimer laser light in addition to halogen lamp light has been researched and developed.
Ext. Abstr. of IWJT, pp23-26, Tokyo (2002) Symposium on VLSI Technology Digest of Technical Papers, pp53-54, Kyoto (2003) Ext. Abstr. of IWJT, pp31-34, Tokyo (2002) Ext. Abstr. of IWJT, pp27-28, Tokyo (2002) 2000 International Conference on Ion Implantation Technology Proceedings, pp. 175-177 (2000) Japanese Patent No. 3054123 US Pat. No. 4,912,065

  However, the conventional method has a problem that the process is complicated, a so-called lead time from when the substrate is loaded to when the processing is completed is large, and expensive equipment is required in each process.

  In view of the above-described conventional problems, an object of the present invention is to provide a method in which impurities can be introduced with inexpensive equipment that has a simple process and a short lead time.

The impurity introduction method according to the first invention of the present application includes a step of performing an amorphized plasma irradiation for bringing the surface of the substrate into an amorphous state, a step of plasma doping impurities to form a shallow junction on the substrate, and a surface of the substrate. An impurity introduction method including annealing to activate the plasma, and in the step of performing amorphization plasma irradiation, the helium gas plasma generated under a pressure of 0.5 atm or more and 1.5 atm or less is applied to the substrate. It is characterized by irradiating the surface.
With such a configuration, since an inexpensive atmospheric pressure plasma processing apparatus (or a plasma processing apparatus that operates near atmospheric pressure) is used, an expensive ion implantation apparatus is not required, and impurities can be introduced at low cost. .

In inventions impurity introducing method of the present application, preferably, when exposed to the plasma of helium gas generated under a pressure of more than 1.5 atm 0.5 atm on a surface of the substrate, placing the substrate It is desirable to supply high frequency power between the substrate electrode and the counter electrode facing the substrate .

  As described above, according to the impurity introduction method of the present invention, impurities can be introduced with inexpensive equipment with a simple process and a short lead time.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
Hereinafter, a first embodiment of the present invention will be described with reference to FIG.

  FIG. 1 shows a cross-sectional view of the plasma processing apparatus used in the first embodiment of the present invention. In FIG. 1, a silicon substrate 2 is placed on a substrate electrode 1. A counter electrode 3 is provided facing the substrate electrode 1, and a shower electrode 4 and a shower plate 5 are provided on the counter electrode 3. The shower electrode 4 and the shower plate 5 are provided with shower holes (through holes) 6 at positions corresponding to each other. A gas is supplied from a gas supply device 7 to a gas reservoir 9 which is a space provided between the counter electrode 3 and the shower electrode 4 via a pipe 8 and is ejected onto the substrate 2 through the shower hole 6. In this state, plasma is generated between the shower plate 5 and the substrate 2 by supplying high frequency power of 13.56 MHz from the high frequency power source 10 to the substrate electrode 1. Each of the above components is in the atmospheric pressure, and a completely sealed and sturdy container such as a vacuum container and a vacuum pump are unnecessary.

  Helium gas is suitable for stably generating atmospheric pressure plasma. The flow rate of helium gas is approximately 10 to 1000 sccm per square centimeter of the substrate area. When the gas flow rate is small, the shower plate 5 is not sufficiently cooled, and arc discharge is likely to occur. If the gas flow rate is too large, the discharge may not ignite. Moreover, it is preferable that the gap G between the shower plate 5 and the board | substrate 2 in FIG. 1 is 0.3 mm-5 mm. If the gap G is too narrow or too wide, the discharge may not ignite. The diameter of the shower hole 6 is preferably 0.05 mm to 1 mm. If the diameter of the shower hole 6 is too small, a change with time when the treatment is repeatedly performed becomes large, which may cause a decrease in reproducibility. If the diameter of the shower hole 6 is too large, arc discharge is likely to occur. The operating pressure range is preferably 0.5 atm or more and 1.5 atm or less. If the pressure is low, a completely sealed container and a vacuum pump are required, which is disadvantageous in terms of cost. Even when the pressure is high, a completely sealed container is required. Operating near atmospheric pressure is most advantageous in terms of cost and total processing time. The high frequency power is supplied in a range of about 0.1 W to 10 W per square centimeter of the substrate area. If the power is too small, discharge may not occur. Conversely, if the power is too large, arc discharge is likely to occur.

  In such a plasma processing apparatus, an atmospheric pressure plasma was generated under the conditions of a helium gas flow rate of 10 slm as an inert gas and a high frequency power of 500 W using a semiconductor substrate 2 having a diameter of 8 inches. By plasma irradiation for 5 seconds, It was possible to make the surface of the semiconductor substrate 2 amorphous by making it amorphous. Subsequently, as a process of plasma doping impurities to form a shallow junction in the semiconductor substrate 2, a conventional doping process using vacuum plasma was performed. Furthermore, in order to activate the surface of the semiconductor substrate 2, flash lamp annealing, which is a conventional technique, was performed. As a result, a shallow junction was successfully formed.

  As described above, in the step of performing amorphization plasma irradiation, amorphization is improved by irradiating the surface of the semiconductor substrate with the plasma of the inert gas generated under the pressure of 0.5 to 1.5 atm. The reason was that the low-energy helium ions acted on the outermost surface of the silicon substrate 2 to destroy the crystal structure of silicon, but only caused a weak action that did not cause sputtering. Conceivable.

(Embodiment 2)
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.

  Since the schematic configuration of the plasma processing apparatus used in the second embodiment of the present invention has already been described with reference to FIG. 1, the description thereof is omitted here.

First, using a conventional ion implantation technique, the surface of the semiconductor substrate 2 having a diameter of 8 inches was implanted, and silicon was implanted to make the surface preamorphous. Next, in the plasma processing apparatus shown in FIG. 1, while supplying 10 sclm of helium gas as an inert gas and 10 sccm of diborane (B ₂ H ₆ ) gas as a gas containing a doping material, atmospheric pressure is applied under the condition of high-frequency power of 300 W. When plasma was generated, boron as an impurity could be introduced into the surface of the semiconductor substrate 2 by plasma irradiation for 4 seconds. Furthermore, in order to activate the surface of the semiconductor substrate 2, flash lamp annealing, which is a conventional technique, was performed. As a result, a shallow junction was successfully formed.

  As described above, in the step of plasma doping with impurities, doping can be performed satisfactorily by irradiating the surface of the semiconductor substrate with plasma of a gas containing impurities generated under a pressure of 0.5 to 1.5 atm. This is probably because low-energy boron ions acted on the outermost surface of the silicon substrate 2 so that boron could be implanted only into an extremely shallow region.

  In addition, instead of irradiating the substrate 2 with atmospheric pressure plasma, it may be possible to introduce impurities by spraying a gas containing impurities onto the substrate under a pressure of 0.5 to 1.5 atm. This method is effective when the impurity concentration to be introduced is low.

(Embodiment 3)
Hereinafter, a third embodiment of the present invention will be described with reference to FIG.

  Since the schematic configuration of the plasma processing apparatus used in the third embodiment of the present invention has already been described with reference to FIG. 1, the description thereof is omitted here.

  First, using a conventional ion implantation technique, the surface of the semiconductor substrate 2 having a diameter of 8 inches was implanted, and silicon was implanted to make the surface preamorphous. Next, as a process of plasma doping impurities to form a shallow junction in the semiconductor substrate 2, a conventional doping process using vacuum plasma was performed. Furthermore, in the plasma processing apparatus shown in FIG. 1, when atmospheric pressure plasma was generated under conditions of a helium gas flow rate of 10 slm as an inert gas and a high frequency power of 900 W, only the surface of the semiconductor substrate 2 was irradiated by plasma irradiation for 1 second. It was possible to heat rapidly and to perform surface annealing. As a result, a shallow junction was successfully formed.

  Thus, in the step of plasma doping with impurities, annealing was successfully performed by irradiating the surface of the semiconductor substrate with plasma of an inert gas generated under a pressure of 0.5 to 1.5 atm. This is probably because low-energy but high-density active particles acted on the outermost surface of the silicon substrate 2 to heat only the very surface in a short time.

(Embodiment 4)
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG.

  Since the schematic configuration of the plasma processing apparatus used in the fourth embodiment of the present invention has already been described with reference to FIG. 1, the description thereof is omitted here.

First, using the semiconductor substrate 2 having a diameter of 8 inches and generating atmospheric pressure plasma under the conditions of a helium gas flow rate of 10 slm as an inert gas and a high frequency power of 500 W, the surface of the semiconductor substrate 2 was exposed to the plasma for 5 seconds. Amorphization to an amorphous state could be performed. Next, in the plasma processing apparatus shown in FIG. 1, while supplying 10 sclm of helium gas as an inert gas and 10 sccm of diborane (B ₂ H ₆ ) gas as a gas containing a doping material, atmospheric pressure is applied under the condition of high-frequency power of 300 W. When plasma was generated, boron as an impurity could be introduced into the surface of the semiconductor substrate 2 by plasma irradiation for 4 seconds. Furthermore, in the plasma processing apparatus shown in FIG. 1, when atmospheric pressure plasma was generated under conditions of a helium gas flow rate of 10 slm as an inert gas and a high frequency power of 900 W, only the surface of the semiconductor substrate 2 was irradiated by plasma irradiation for 1 second. It was possible to heat rapidly and to perform surface annealing. As a result, a shallow junction was successfully formed.

  Thus, since the three steps of amorphization, doping, and annealing can be performed using atmospheric pressure plasma, it has been shown that the steps are simple, the lead time is short, and impurities can be introduced with inexpensive equipment.

(Embodiment 5)
Hereinafter, a fifth embodiment of the present invention will be described with reference to FIG.

  FIG. 2 is an improvement of the plasma processing apparatus shown in FIG. 1 and can perform the three steps of amorphization, doping, and annealing more uniformly. In FIG. 2, a substrate (not shown) is placed on the substrate electrode 1. The counter electrode 3 is fixed to the handler 11. The structure between the counter electrode 3 and the substrate electrode 1 is the same as that shown in FIG. 1, and many shower holes are provided. The handler 11 is fixed to the bracket 12, and the bracket 12 is fixed to the slider 13. The slider 13 can move on the rail 14 and can move from the bracket 12 to the counter electrode 3 in the direction of the arrow. The rail 14 is fixed to the slider 15. The slider 15 can move on the rail 16 and can move from the rail 14 to the counter electrode 3 in the direction of the arrow. That is, with this structure, the counter electrode 3 can move in xy parallel to the substrate electrode 1 and the substrate.

  It is not easy to generate a microscopically uniform plasma at atmospheric pressure, and what appears to be a uniform discharge at first glance is often a collection of minute streamer discharges. In such a case, it is difficult to perform a uniform process over the entire surface of the semiconductor substrate. Therefore, when performing plasma processing using a plasma processing apparatus having a structure as shown in FIG. 2, it is effective to move the counter electrode 3 in parallel with respect to the substrate electrode 1 and the substrate. That is, streamer discharge can be generated on the surface in average, and the uniformity of processing can be improved. The amplitude of the xy motion is preferably about 0.1 mm to 10 mm, and the frequency of the xy motion is preferably about 1 to 100 Hz. If the amplitude is smaller than 0.1 mm, it is difficult to disperse the streamer discharge and to generate it in the plane on the average. On the contrary, if it is larger than 10 mm, there is a drawback that the vibration device becomes large. If the frequency is less than 1 Hz, it is difficult to disperse the streamer discharge and to generate it in the plane on average. On the other hand, if the frequency is higher than 100 Hz, there is a disadvantage that the vibration device becomes large.

(Embodiment 6)
Hereinafter, a sixth embodiment of the present invention will be described with reference to FIG.

  FIG. 3 shows a cross-sectional view of the plasma processing apparatus used in the sixth embodiment of the present invention. In FIG. 3, a silicon substrate 2 is placed on the substrate electrode 1. A counter electrode 3 is provided facing the substrate electrode 1, and a shower electrode 4 and a shower plate 5 are provided on the counter electrode 3. The shower electrode 4 and the shower plate 5 are provided with shower holes (through holes) 6 at positions corresponding to each other. A gas is supplied from a gas supply device 7 to a gas reservoir 9 which is a space provided between the counter electrode 3 and the shower electrode 4 via a pipe 8. An insulating plate 17 is provided between the counter electrode 3 and the shower electrode 4, and the shower electrode 4 is grounded. In this state, by supplying high frequency power of 13.56 MHz from the high frequency power source 10 to the counter electrode 3, plasma is generated in the gas reservoir 9 between the insulating plate 17 and the shower electrode 4. Each of the above components is in the atmospheric pressure, and a completely sealed and sturdy container such as a vacuum container and a vacuum pump are unnecessary. Active particles generated by the plasma are ejected onto the substrate 2 through the shower holes 6.

  Helium gas is suitable for stably generating atmospheric pressure plasma. The flow rate of helium gas is approximately 10 to 1000 sccm per square centimeter of the substrate area. When the gas flow rate is small, the shower plate 5 is not sufficiently cooled, and arc discharge is likely to occur. If the gas flow rate is too large, the discharge may not ignite. Moreover, it is preferable that the gap G between the shower plate 5 and the board | substrate 2 in FIG. 3 is 0.1 mm-50 mm. Unlike the configuration of FIG. 1, since the discharge occurs in the gas reservoir 9, the gap G can be set in a relatively wide range. Further, since the plasma does not directly touch the substrate 2, there is an advantage that charge-up damage and the like hardly occur, and further, uniform processing can be performed. However, the general processing speed is inferior to the configuration of FIG. The diameter of the shower hole 6 is preferably 0.05 mm to 1 mm. If the diameter of the shower hole 6 is too small, a change with time when the treatment is repeatedly performed becomes large, which may cause a decrease in reproducibility. If the diameter of the shower hole 6 is too large, arc discharge is likely to occur. The operating pressure range is preferably 0.5 atm or more and 1.5 atm or less. If the pressure is low, a completely sealed container and a vacuum pump are required, which is disadvantageous in terms of cost. Even when the pressure is high, a completely sealed container is required. Operating near atmospheric pressure is most advantageous in terms of cost and total processing time. The high frequency power is supplied in a range of about 0.1 W to 10 W per square centimeter of the substrate area. If the power is too small, discharge may not occur. Conversely, if the power is too large, arc discharge is likely to occur.

First, using a conventional ion implantation technique, the surface of the semiconductor substrate 2 having a diameter of 8 inches was implanted, and silicon was implanted to make the surface preamorphous. Next, in the plasma processing apparatus shown in FIG. 3, while supplying 10 sclm of helium gas as an inert gas and 10 sccm of diborane (B ₂ H ₆ ) gas as a gas containing a doping material, atmospheric pressure is applied under the condition of high frequency power of 400 W. When plasma was generated, boron as an impurity could be introduced into the surface of the semiconductor substrate 2 by plasma irradiation for 10 seconds. Furthermore, in order to activate the surface of the semiconductor substrate 2, flash lamp annealing, which is a conventional technique, was performed. As a result, a shallow junction was successfully formed.

  As described above, in the step of plasma doping with impurities, doping can be performed satisfactorily by irradiating the surface of the semiconductor substrate with plasma of a gas containing impurities generated under a pressure of 0.5 to 1.5 atm. This is probably because boron radicals acted on the outermost surface of the silicon substrate 2 so that boron could be implanted only in a very shallow region.

  In the embodiment of the present invention described above, only a part of various variations with respect to the shape of the counter electrode and the substrate electrode, the method and arrangement of the plasma source, etc., are illustrated in the scope of application of the present invention. It goes without saying that various variations other than those exemplified here can be considered in applying the present invention.

  Moreover, although the case where plasma was generated using high frequency power of 13.56 MHz was illustrated, it is possible to generate plasma using high frequency power from several hundred kHz to several GHz. Alternatively, DC power may be used, or pulse power may be supplied. When pulse power is used, there is an advantage that an inert gas is unnecessary in the doping process.

  An inert gas other than helium may be used, and at least one of neon, argon, krypton, and xenon (xenon) can be used. These inert gases have the advantage that the adverse effect on the sample is smaller than other gases. In addition, by using xenon, ultraviolet rays including vacuum ultraviolet light can be generated and the treatment can be performed effectively.

  Further, although the case where the sample is a semiconductor substrate made of silicon has been exemplified, the present invention can be applied when processing samples of various other materials.

  Further, although the case where the impurity is boron is illustrated, the present invention is effective when the sample is a semiconductor substrate made of silicon, particularly when the impurity is arsenic, phosphorus, boron, aluminum, or antimony. This is because a shallow junction can be formed in the transistor portion.

The present invention is effective when the doping concentration is low, and is particularly effective as a plasma doping method aiming at 1 × 10 ¹¹ / cm ^{2 to} 1 × 10 ¹⁷ / cm ² . In addition, as a plasma doping method aiming at 1 × 10 ¹¹ / cm ^{2 to} 1 × 10 ¹⁴ / cm ² , there is a particular effect.

  According to the impurity introduction method of the present invention, the process is simple, the lead time is short, and the impurity can be introduced with inexpensive equipment. It can also be applied to applications such as semiconductor impurity doping, manufacturing thin film transistors used in liquid crystals, and surface modification of various materials.

Sectional drawing which shows the structure of the plasma processing apparatus used in 1st, 2nd, 3rd and 4th embodiment of this invention. The perspective view which shows the structure of the plasma processing apparatus used in 5th Embodiment of this invention. Sectional drawing which shows the structure of the plasma processing apparatus used in 6th Embodiment of this invention. Sectional drawing which shows the structure of the plasma processing apparatus used by the prior art example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate electrode 2 Substrate 3 Counter electrode 4 Shower electrode 5 Shower plate 6 Shower hole 7 Gas supply device 8 Piping 9 Gas reservoir 10 High frequency power supply G Gap

Claims (2)

Impurity introduction including a step of performing amorphization plasma irradiation for bringing the surface of the substrate into an amorphous state, a step of plasma doping impurities to form a shallow junction on the substrate, and a step of annealing to activate the surface of the substrate A method,
A method for introducing an impurity, comprising: irradiating a surface of a substrate with plasma of helium gas generated under a pressure of 0.5 to 1.5 atm in the step of performing amorphized plasma irradiation. When exposed to the plasma of the helium gas to the surface of the substrate, and the substrate electrodes for mounting the substrate, impurity introduction may claim 1 Symbol mounting, characterized in that supplying high-frequency power between counter electrode opposed to the substrate Method.

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